Reciprocating pumps operate to move fluid using one or more oscillating pistons, plungers, or membranes while valves selectively restrict the fluid to move to a desired direction. Reciprocating pumps are used in many applications, such as mobile utility vehicles. Examples of such mobile utility vehicles include sewer cleaners and hydro-excavators, which can be collectively referred to as debris collection vehicles. In certain examples, debris collection vehicles typically have one or more reciprocating displacement pump as a water pump.
Reciprocating displacement pumps can be controlled by a shifting mechanism. The shifting mechanism operates to control alternating movements of one or more piston (double acting) or plunger (single acting) reciprocating in a pump. In certain examples, the shifting mechanism includes one or more mechanical elements, such as mechanical linkages and proximity switches, to find the location of a moving piston or plunger near the dead center thereof within an associated cylinder and change the direction of the piston or plunger in each stroke. An example of the shifting mechanism is disclosed in U.S. Pat. No. 3,700,360, the entirety of which is incorporated herein by reference.
In general, it is desirable to increase a stroke length of a piston within a cylinder to prolong a product life and increase fuel efficiency. To maximize the stroke length of a piston, a shifting position of the piston within the cylinder needs to be arranged as close as possible to an end of the cylinder to reduce the number of strokes at a given flow rate. Setting the shifting position of the piston away from the end of the cylinder shortens the stroke length of the piston and therefore increases the number of piston strokes to fulfill the same flow rate. On the other hand, setting the shifting position of the piston too close to the end of the cylinder can cause the piston to hit the end of the cylinder as the piston changes the direction of stroke. The piston hitting the end of the cylinder as it shifts its direction can damage several mechanical parts, such as piston and cylinder components. Further, such collision of the piston against the cylinder end leads to a pressure spike on hydraulic system and causes cooling components to fail.